How the Fewest Become the Greatest. L. casei’s Impact on Long Ripened Cheeses

Abstract

Members of the Lactobacillus casei group, including species classified currently as L. casei, L. paracasei, and L. rhamnosus, are among the most frequently found species in raw milk, hard cooked, long-ripened cheeses. Starting from very low numbers in raw milk, they become dominant in the cheese during ripening, selected by physical and chemical changes produced by cheese making and ripening. Their presence at different stages of cheese making and ripening is crucial in defining product features. For these reasons, the scientific community has been more and more interested in studying these “tiny but mighty microbes” and their implications during cheese making and ripening. The present paper reviews the current literature on the effect of L. casei in cheeses, with particular reference to the case of Parmigiano Reggiano and Grana Padano, two of the most famous PDO (Protected Designation of Origin) Italian cheeses. Recent advances regarding the selection of new wild strains able to persist until the end of ripening and carrying out slow but crucial activities resulting in specific aromatic features, are also presented.

The Interrelationship Between Microbiota and Peptides During Ripening as a Driver for Parmigiano Reggiano Cheese Quality

“…This is likely due to the prevalence of SLAB coming from the starter, which, although prepared differently by each dairy, generally contains mainly L. helveticus and L. delbrueckii and possibly S. thermophilus and L. fermentum ( Bottari et al, 2010 , 2013 ; De Filippis et al, 2014 ; Bertani et al, 2020 ). Major differences revealed among dairies between 1 and 2 months old samples and 7 and 9 months old samples, are consistent with the growth of NSLAB coming mainly from raw milk and their higher adaptability to specific environmental conditions, driven by cheese making parameters ( Bottari et al, 2018 ). In the following ripening stages, biodiversity indices presented some differences according to the investigation method: while metataxonomic data showed a consistent increase of all the indicators until 9 months of ripening, LH-PCR performed on entire bacterial cells indicates that there is a decrease in richness and diversity after 2 months of ripening.…”

“…Curds from all dairies were, in fact, dominated by the species L. helveticus and L. delbrueckii , which derive from the natural whey starter used for cheese making ( De Filippis et al, 2014 ; Bertani et al, 2020 ). After the brining step (1-month-old samples and later), a compositional change occurs in cheese microbiota that shows a decrease in the relative abundance of the SLAB species, while NSLAB population, initially present at low abundances, find suitable conditions for development ( Lazzi et al, 2014 ; Bottari et al, 2018 ). Indeed, after 6 months of ripening, cheeses from all dairies showed an increase of Lacticaseibacillus , which is known to dominate the microbiota of PR cheese during ripening ( Gatti et al, 2014 ).…”

Peptide Profiling and Biological Activities of 12-Month Ripened Parmigiano Reggiano Cheese

“…PR is a hard cheese with protected designation of origin (PDO), made by a combination of partially skimmed and whole raw milk added with natural whey starter, principally made up by thermophilic S-LAB [ 9 ]. After cooking and brine salting, PR is subjected to at least 12 months of ripening, during which NS-LAB progressively replaces the S-LAB population [ 10 ]. The production and maturation procedures of the PR cheese, according to the PDO, are detailed in Tagliazucchi et al [ 11 ].…”

Phenotypic Diversity of Lactobacillus casei Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters

“…Strains with a longer Lag phase are favored in the selection, since they require longer time to adapt to the milk environment, thus avoiding competition in acidification with the starter culture [19]. This is what occurs in the cheese making processes where bacteria belonging to the L. casei group are present at low abundances in the vat milk, and remain basically unchanged in number in the first stages of the manufacturing, allowing the natural whey starter to acidify the curd [13][14][15]. For this reason, impedance analysis can provide useful criteria to screen among a wide set of potentially interesting strains [20,25].…”

“…An example of the interplay between SLAB and NSLAB in dairy microbiota can be found in long-ripened traditional Italian cheeses, such as Parmigiano Reggiano and Grana Padano, that are produced using raw milk and a natural whey starter [13,14]. The use of raw milk leads to the introduction of microorganisms belonging to the Lactobacillus casei group; these are initially present in low numbers, but they increase in the subsequent cheese-making steps, and retain viability throughout the ripening time [15]. The L. casei group includes three species, Lactobacillus paracasei, Lactobacillus casei and Lactobacillus rhamnosus.…”